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Special Issue "Advances of GaN-Based Semiconductor Materials"

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Guest Editor

Electron Microscopy Laboratory, School of Physics, Peking University, Beijing 100871 China
Interests: Ⅲ-Nitride;TEM; EELS; defect; phonon

Dr. Fang Liu

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Guest Editor

State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, Beijing 100871, China
Interests: III-nitride films; epitaxial growth; optoelectronic devices

Special Issue Information

Dear Colleagues,

GaN-based semiconductor materials have obtained tremendous attention due to their appealing applications in solid-state lighting and power devices. They are critical to the development of next-generation optoelectronic and electronic devices. Additionally, recent advances of nitride ferroelectrics (e.g., ScAlN and ScGaN) are promising to the new-generation microelectronic memory, acoustic devices, and quantum devices, which will accelerate the multifunctional and integrated develpment of ferroelectric functionality and microelectronics. To obtain high-quality GaN materials is of great significance for practical applications of devices. However, some of growth mechanisms of GaN are still unclear, especially, the mechanisms of GaN grown on foreign substrates (e.g., sapphire, two-dimensional materials, and metal, etc.).

We aim to investigate the epitaxial growth mechanisms of nitride semiconductors, which include novel epitaxial mechanisms and structural features, such as domain merging, defect evolution, lattice polarity, and so on. In addition, the relationship of microstructures and physical properties (e.g., electronic, phonon, and thermal properties), particularly in the scale of nanometers, is deserved to be comprehensively investigated. This Special Issue will also cover works relating to relative applications of GaN-based devices.

Dr. Tao Wang
Dr. Fang Liu
Guest Editors

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Keywords

III-nitride semiconductors
epitaxy
defect
device
nanoscale
lattice polarity
thermal management
polarizations
ferroelectrics
TEM
EELS

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Research

Open AccessArticle

Energetics of Interfaces and Strain Partition in GaN/AlN Pseudomorphic Superlattices

Theodoros Karakostas

Philomela Komninou

and

Vassilis Pontikis

Crystals 2023, 13(8), 1272; https://doi.org/10.3390/cryst13081272 - 17 Aug 2023

Viewed by 413

Abstract

We present the results of a twofold experimental and computational study of (0001) GaN/AlN multilayers forming pseudomorphic superlattices. High-Resolution Transmission Electron Microscopy (HRTEM) shows that heterostructures with four c-lattice parameters thick GaN Quantum Wells (QW) are misfit-dislocation free. Accurate structural data are extracted from HRTEM images via a new methodology optimizing the residual elastic energy stored in the samples. Total energy calculations are performed with several models analogous to the experimental QWs with increasing thicknesses of GaN, whereas this of the AlN barrier is kept fixed at n = 8 c-lattice parameters. With vanishing external stresses, minimum energy configurations of the studied systems correspond to different strain states. Linear elasticity accurately yields the corresponding lattice parameters, suppressing the need for on-purpose total energy calculations. Theoretically justified parabolic fits of the excess interfacial energy yield the values of interfacial stress and elastic stiffness as functions of the GaN QW thickness. Total species-projected densities of states and gap values extracted from there allow deciphering the effect of the evolving strain on the electronic structure of the superlattice. It is found that the gap energy decreases linearly with increasing the strain of the QW. These results are briefly discussed in the light shed by previous works from the literature. Full article

(This article belongs to the Special Issue Advances of GaN-Based Semiconductor Materials)

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Transition from Screw-Type to Edge-Type Misfit Dislocations at InGaN/GaN Heterointerfaces

and

Crystals 2023, 13(7), 1027; https://doi.org/10.3390/cryst13071027 - 28 Jun 2023

Cited by 1 | Viewed by 400

Abstract

We have investigated the interface dislocations in In_xGa_1−xN/GaN heterostructures (0 ≤ x ≤ 0.20) using diffraction contrast analysis in a transmission electron microscope. The results indicate that the structural properties of interface dislocations depend on the indium composition. For lower indium composition (up to x = 0.09), we observed that the screw-type dislocations and dislocation half-loops occurred at the interface, even though the former do not contribute toward elastic relaxation of the misfit strain in the InGaN layer. With the increase in indium composition (0.13 ≤ x ≤ 0.17), in addition to the network of screw-type dislocations, edge-type misfit dislocations were generated, with their density gradually increasing. For higher indium composition (0.18 ≤ x ≤ 0.20), all of the interface dislocations are transformed into a network of straight misfit dislocations along the <10–10> direction, leading to partial relaxation of the InGaN epilayer. The presence of dislocation half-loops may be explained by a slip on basal plane; formation of edge-type misfit dislocations are attributed to punch-out mechanism. Full article

(This article belongs to the Special Issue Advances of GaN-Based Semiconductor Materials)

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